Method for making a laminated glass sheet

ABSTRACT

In a method for making laminated glass, a sheet includes two glass substrates with an interlayer sheet between them. This sheet includes a polymer based film provided on one of the surfaces with a thin functional layer. The sheet is cut out in dimensions substantially identical to or greater than one of the glass substrates. The sheet is slit on at least the thickness of the film provided with the functional layer so as to delimit at least a peripheral zone of the film located between the slitting line and its edge. The interlayer sheet is assembled between the glass substrates. The peripheral zone is then detached by mechanical traction to transform the laminated glass sheet.

CROSS REFERENCE TO RELATED APPLICATION

This application is a division of U.S. Application Ser. No. 09/147,419,now U.S. Pat. No. 6,352,754.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a process for manufacture of laminatedglazing units, especially those designed as equipment for vehicles ofthe windshield type. It relates more particularly to laminated glazingunits in which the intermediate film, which is a polymer-base materialdisposed between rigid substrates, generally of glass, is provided witha coating having thermal properties, especially of reflection in theinfrared, thus endowing these glazing units with a highly satisfactoryfunction of protection against solar radiation.

2. Discussion of the Background

Such configurations of glazing units are known in particular from thefollowing patents: U.S. Pat. No. 4,639,069, U.S. Pat. No. 4,369,945, EP0303586 and WO 90/08334, wherein there are used intermediate filmsgenerally comprising a ply of transparent polymer of the polyethyleneterephthalate type (PET), provided on one of its faces with the coatingwhich reflects in the infrared, said ply being inserted between twoplies of thermoplastic polymer of the polyvinyl butyral type (PVB)before the usual assembly of this multi-layer intermediate film togetherwith the two glass substrates is performed.

A problem specific to this type of configuration soon became apparent,however: in choosing these “multi-layer intermediate films”, withdimensions identical to those of the glass plates, theinfrared-reflecting coating was disposed flush with the edge wall of theglass plates. This coating usually comprises layers which aresusceptible to deterioration, especially to oxidation, in contact withmoisture. This is particularly true for metallic layers, especially ofsilver, which tend to corrode along their periphery, such corrosionprogressively spreading over their entire surface and leading to opticaldefects and loss of thermal performances.

Suggestions toward solving this problem have already been made. Forexample, U.S. Pat. No. 5,131,967 describes a technique using the laserto margin the reflecting coating deposited on the PET, thus preventingit from occupying a flush position. This technique seems to becumbersome, however, and it substantially lengthens the production time,since the laser must achieve ablation of the reflecting coating over aperipheral strip of non-negligible width.

Another suggestion was made in U.S. Pat. No. 5,320,893: this documentteaches making a cut in the thickness of the PET ply, around theperiphery thereof, so that the peripheral corrosion of the reflectingcoating will be stopped from spreading by this break line. It is notcertain that a simple line will be able to prevent all spreading ofcorrosion in this way.

SUMMARY OF THE INVENTION

The purpose of the invention is therefore new processes for manufactureof this type of glazing unit, wherein the quality of the reflectingcoating is preserved in the zones of visibility, while the aforesaiddisadvantages are remedied, in particular while being relatively simpleto use and at the same time having great efficacy and reliability.

The primary object of the invention, therefore, is a first process formanufacture of a laminated glazing unit comprising at least two rigidsubstrates of the glass type assembled by an intermediate filmcomprising at least one ply based on a polymer or polymers provided onat least one of its faces with a thin layer or a stack of thin layershaving thermal properties, especially properties of reflection in theinfrared. This process includes the following stages:

-   -   a)—the intermediate film in “complete” form or already        containing at least the ply provided with the thin layer or        layers is cut to dimensions essentially identical to or larger        than those of at least one of the two substrates,    -   b)—the said intermediate film is incised through at least the        thickness of the ply provided with the thin layer or layers, in        such a way as to define, in the said ply, at least one        peripheral zone localized between the incision line and the edge        thereof,    -   c)—the intermediate film is assembled in “complete” form between        the two substrates possibly by adjoining thereto any polymer ply        or plies thereof which was or were missing in case it was not        previously in “complete” form,    -   d)—the peripheral zone or zones is or are detached from the        intermediate film by pulling them mechanically,    -   e)—the laminated glazing unit is then transformed.

Here and throughout the text hereinafter, the thin layer or layershaving thermal properties, especially properties of reflection in theinfrared, will be referred to as the “functional layer or layers”. Underthis term, the invention also comprises one or more thin layers whichmay also have other properties, especially optical or electrical, inaddition to or instead of thermal properties.

Within the meaning of the invention, “assembly” is understood as theoperation comprising correctly positioning all the elements of thelaminated glazing unit correctly relative to each other beforeperforming the operation in which they are finally unified.

Within the meaning of the invention, “transformation” is understood asthe unification operation, which is generally performed with applicationof pressure and input of heat.

Finally, the intermediate film has already been described as beingcomplete or not complete in stage a). Within the meaning of theinvention, “complete” must be understood as the intermediate filmalready containing all the polymer plies of the final laminated glazingunit, in particular a sequence of the type PVB/PET/functional layer orlayers/PET/PVB (or in other words the polymer support of the functionallayer or layers already embraces the two plies of polymer ofthermoplastic type that will permit assembly thereof with the rigidsubstrate or substrates of the window-glass type in the final glazingunit). In stage a), it may already be in complete form and contain allof these plies. However, it may also be incomplete, containing only partthereof, the remaining polymer plies then being added during assembly,while superposing them on the “incomplete” intermediate film which hasbeen incised according to stage b).

The “incomplete” intermediate film on which the incision is made maytherefore contain only the sequence of the type PVB/PET/functional layeror layers (or in other words the polymer support provided with thefunctional layer or layers alone or combined in only one of the plies ofthermoplastic polymer that will permit assembly thereof with awindow-glass substrate or substrates).

In general, therefore, the process according to the invention comprisesstages (a) to (e).

According to a first variant, the stages are performed successively inthe order in which they were listed hereinabove.

According to a second variant, the order in which these stages areperformed may be modified, in particular by reversing the order ofstages (c) and (d), or in other words by removing the peripheral zonesof the intermediate film incised according to stage (a) beforeproceeding with assembly. In this way it is possible, in particularlypreferred manner, to perform incision according to stage (a) of theincomplete intermediate film, especially of the type PVB/PET/functionallayer or layers, then to detach the incised zones, before adjoining tothe intermediate film its second PVB ply and assembling it with the twowindow-glass substrates. (Here and throughout the text hereinafter, thespecific term PVB, which is merely an example, must be understood as anyply of thermoplastic polymer, while the specific term PET must beunderstood as any ply of polymer of flexible type capable of beingprovided with a functional layer or layers).

The process according to the invention is particularly advantageous: infact, in the completed laminated glazing unit, the ply provided with thereflecting coating is effectively “margined” when the incision linefollows its entire periphery, the margining having been performed insuch a way that the reflecting coating (the functional thin layer orlayers) is no longer disposed flush with the edge wall of the glassplates, thus considerably reducing and even completely eliminating therisks of corrosion via the edge walls.

The technique of the invention in fact permits “selective” margining, inthe sense that the form of the incision line or lines can be modulatedspecifically in such a way that the margining for each configuration ofglazing unit is matched to the scope of corrosion risks. Thus themargining can be chosen over a more or less broad peripheral strip ofthe ply depending on the glazing unit. In addition, in one and the sameglazing unit, the width and form of the peripheral zones which willdefine margining of the ply can be varied, for example in order to“outline” the planned placement between substrates and ply of elementswhich tend to pose corrosion risks or to create weak spots in theperipheral imperviousness, for example, as will be detailed hereinafter,elements for connecting circuitry, sensors, radio antennas, or in orderto allow for special geometric forms of the glazing units.

The technique according to the invention is therefore particularlyflexible and permits margining which is particularly modulablegeometrically and particularly precise. Thus the incision line or linesmay be chosen so as to follow the form of the edge walls of thesubstrates very precisely, in smaller proportions, especially in such away that the ply, once the glazing unit is completed, has the sameroundings at the corners as do the substrates themselves, giving a fullyesthetic impression. It is also possible to provide broader margining inthe zones in which the edge walls of the glass plates have very specificforms, for example pointed forms, which may create weak points forattack by moisture.

The technique of the invention is in addition easy to use, mostparticularly during the assembly phase. In fact, it is easy to positionthe intermediate film correctly relative to the two glass plates, sincethe intermediate film is at least as large as those plates. (If larger,it is merely necessary to perform final clipping). It is a little moredifficult to have to position an intermediate film which has alreadybeen margined and has smaller dimensions than those of the two glassplates, because in this case an almost constant distance relative to theedge walls of the glass plate must be provided all around its periphery.

Advantageously, the ply provided with the reflecting thin layer orlayers is based on a flexible polymer or polymers, usually transparentor substantially transparent, especially belonging to the polyesterfamily, of the linear polyester type, such as polyethylene terephthalate(PET), polycarbonates, polypropylene, polyethylene, polyether sulfides,polysulfides, and in general polymethacrylates. PET is particularlysuitable for this application.

Preferably the intermediate film is “composite” in the sense that itcomprises a plurality of polymer-base plies. Advantageously it has aconfiguration in which the ply provided with the thin layer or layers,especially of PET, is disposed between at least two plies based on athermoplastic polymer or polymers, which are well suited to assembly bylamination together with rigid substrates of the glass type. Moreparticularly, the plies can be based on polyvinyl butyral (PVB) or on apolyurethane or polyurethanes (PU).

In the case of such a “composite” intermediate film, when an incision ismade in the ply provided with the thin layer or layers in stage (b), anincision is simultaneously made in the ply or plies topping it (andpossibly to some extent in the underlying plies as well). In fact, thesimplest approach is to perform this stage (b) on the completeintermediate film, once all of its constitutive plies have beenassembled. Incision of plies “above” the functional ply with a thinlayer or layers does not pose any problem of peripheral imperviousness.In fact, during mechanical detachment of the functional ply in stage(d), especially when it comprises PET, the ply or plies associatedtherewith in the intermediate film, of PVB type, and which themselvesmay have been incised during stage (b), remain in place between the tworigid substrates: during transformation, generally using at the sametime means of the suction ring type for applying peripheral vacuum,means for applying pressure on the glazing unit and heating means, inthe case of a composite intermediate film of the PVB/PET/PVB type, thetwo PVB plies joined together in the peripheral zones where the PET plyhas been removed coalesce with each other, thus creating an imperviousseam relative to the edge of the PET ply provided with the thin layer orlayers. Preferably, during stage (d), only the peripheral zone or zonesof the ply provided with a layer or layers is or are detached. It mustbe noted that, in the case of an intermediate film of the PVT/PET/PVBtype, the incision stage can be performed on the “incomplete”intermediate film comprising two-ply PVB/PET, and the second ply of PVBwill then be added during assembly.

The incision according to stage (b) can be performed in different ways:a cut can be provided by stamping or by a movable tool provided with aslicing element of the blade or laser type. This latter variant is moreadvantageous, because the movement of the movable tool can be controlledin automated manner by modifying its path and/or its cutting depth asdesired, along the desired incision line or the dimensions of thelaminated glazing unit to be fabricated, by simple reprogramming of themovable tool by computerized/electronic means. In particular, cuttingdevices of the type sold commercially by the ARISTO or ZÜOND companiescan be used.

As regards the choice of the layer or stack of layers designed to endowthe glazing unit with thermal properties, especially reflection in theinfrared, there can be chosen at least one substantially metallic layer,especially based on at least one of the following metals: silver,copper, gold, nickel, chromium, indium, tantalum, niobium, aluminum,especially an alloy of the nickel-chromium type or one belonging to thefamily of steels, or else one based on a metal nitride of the type TiN,ZrN or else based on doped metal oxide or oxides such as tin oxide dopedwith fluorine (SnO₂:F) or indium oxide doped with tin (ITO). In fact,the criterion is such that the layers can be deposited on polymersubstrates of PET type by known techniques.

There can be used a single layer of this type or a plurality separatedby layers based on dielectric materials of the metal oxide type (Nb₂O₅,Ta₂O₅, ZnO, In₂O₃, TiO₂, SnO₂, Al₂O₃, WO₃, etc.) or nitride of the Si₃N₄type or other materials of the MgF₂ type.

For more information on stacks of this type, it is possible inparticular to consult European Patent EP 0438357, which describes alayer based on tantalum, European Patent EP 0511901, which describes alayer based on nickel-chromium alloy, steel or tantalum associated withdielectric layers of the SnO₂, TiO₂, Ta₂O₅ type. It is also possible toconsult European Patents EP 0506507, EP 0611213, EP 0636587, EP 0678484,EP 0718250 for stacks which use a layer of silver between at least twolayers of dielectric material, or else European Patent EP 0638528 forstacks which use two layers of silver with a layer or layers ofdielectric material interposed therebetween.

To facilitate detachment by mechanically pulling the “incised”peripheral zones of the ply provided with the thin layer or layersduring stage (d), it can be advantageously provided that theseperipheral zones have dimensions such that they locally “overhang” theedge walls of the rigid substrates once the intermediate film has beenpositioned therebetween, especially in the form of a starting tab ortabs on which it is easy to exert mechanical pulling action to detachthe said peripheral zones. To facilitate detachment, it is preferable toprovide these tabs in the extension of at least one of the edges of theglass plates.

According to a particular variant of the invention, it can be providedthat the thin layer or layers having thermal properties is or areprovided with electricity supply means. In this way they can be endowedas desired with a heating-layer function, which is particularly usefulfor demisting or deicing the glazing units, especially thoseconstituting equipment of vehicles of the windshield type, wherevisibility is imperative. What then remains is development of theplacement of the connecting circuitry permitting them to be suppliedwith electricity, in such a way that the operation of detachment of theperipheral zones during stage (s) of the process of the invention doesnot cause damage.

According to another variant of the invention, it is also possible toprovide, in one of the faces of at least one of the plies whichconstitutes the intermediate film and which is not in contact with thelayer or layers having thermal properties, a heating layer or a networkof heating wires together with their appropriate connecting circuitry.The simplest configuration, in an intermediate film of typePVB/PET/layer or layers having thermal properties/PVB, consists ofproviding on one of the faces of the PVB designed to be placed incontact with the rigid substrate of the glass type, a network of heatingwires which is caused in known manner to become “inlaid” on its surface.This network, again in known manner, is supplied by oppositely disposedcurrent leads which are sometimes called “busbars” and are made ofstrips of metal of the copper type. The dimensions of this network andthe positioning of these “busbars” with respect to the edge of thelaminated glazing unit can remain identical to the dimensions andpositionings of this type of heating network of a “standard” laminatedunit, where the intermediate film is made merely of one thermoplasticply of the PVB type. In fact, according to the process of the invention,only the ply of the intermediate film which is provided with the thinlayer or layers having thermal properties is “margined” in the finallaminated glazing unit, while the other polymer plies associatedtherewith, especially that of PVB, remain in place and have dimensionsadjusted exactly to those of the two glass plates. Advantageously, thenetwork of heating wires is dimensioned in such a way as to be spaced byat most 1 cm, especially about 6 to 8 mm, from the edge wall of theglass substrates of the glazing unit once it has been laminated.

The “incision line” in the ply provided with the layer or layers havingthermal properties, which will determine the peripheral zones to beultimately detached from the said ply, can have very varied profilesdepending on the needs. Thus, in the simplest configuration, it can“follow”, at least partly and in smaller proportions, a profile which isidentical or close to that of the edge walls of the rigid substrates ofthe glass type. In this way there is achieved margining of the ply whichis esthetic, regular, extremely precise and which can easily conform toand follow the “roundings” of the glass plates.

The said line can therefore be chosen in such a way that, once assemblyhas been completed, there exists, between the edge wall of the ply andthe edge walls of the rigid substrates of the glass type, a margin whichis always at least 3 mm, especially at least 5 mm, preferably about 6mm. In this way there is assured sufficient distance between the edgesof the thin layer or layers having thermal properties and the edges ofthe glazing unit itself, thus avoiding any risk of corrosion of thelayer or layers via the edges.

Although the laminated glazing unit is more complex in the sense that itcontains elements inserted between the glass substrates and theintermediate film, it is possible as a consequence to adapt the incisionline in such a way that it “enclaves” the said elements: once theperipheral zones have been detached along this line, these elements willtherefore be in contact with the plies of the intermediate film whichare not provided with the layer or layers having thermal properties, andthe ply provided with this layer or these layers has dimensions suchthat it “outlines” them. The advantage once again is to protect the thinlayer or layers in the zones where it or they would be more susceptibleto corrosion attack, due to penetration of moisture, for example,especially such zones in which elements in addition to the materialsspecific to the laminated glazing unit are present. Such elements caninclude all the elements of the connecting circuitry, for example thosecited hereinabove for supplying a network of heating wires, moreparticularly in the junction zone between the collectors (busbars) andthe current leads. They can also be sensors of types such as volumetricsensors, moisture sensors, ultrasonic sensors, sensors of the type usedin remote toll-charge recording. They can also be electronic elements ofthe electronic chip type, or wave transmitter/receiver elements of theradio antenna type.

According to one variant of the invention, it is also possible, duringstage b) of incision of the intermediate film, to provide for incisionsto be made along a closed line, to create “windows” in the central part,or in other words not at the periphery, of the ply provided with itsthin layer or layers.

Once these “windows” have been incised, they can be manually detachedfrom the intermediate film before the assembly stage. This internalmargining makes it possible to insert diverse elements in thenon-peripheral portion, especially all types of sensors, electronicelements cited hereinabove, such as remote sensors for toll-chargerecording or antenna elements for systems such as the “G.P.S.” (atechnique of identifying locations by satellite, otherwise known as“Global Positioning System”. It has also proved useful without addingany element in the “window” thus created, especially for use as a windowwhich allows electromagnetic waves to pass (application to remotetoll-charge recording).

According to the invention, it is possible during stage (d) to providefor masking, by means of an opacifying coating, of all or part of thezones of the intermediate film corresponding to the zones (“windows”and/or border of the ply) extracted from the ply provided with the layeror layers having thermal properties. This coating can be depositeddirectly on one of the faces of one of the glass substrates, especiallyby deposition of enamel. The deposit can be applied on the outwardlydirected glass face or on the glass face designed to be located on theside next to the intermediate film, this latter type of deposit beingdescribed in particular in International Patent WO-94/22779. Theopacifying coating can also be deposited by an ink-jet or silk-screenprinting technique, on one of the glass plates or on one of the faces ofone of the polymer-base plies associated with the ply provided with thethin layer or layers having thermal properties in the intermediate film.It can also be a deposit of opaque paint, especially one based onpolyurethane. If this deposit is applied on the glass face turned towardthe intermediate film, it is useful to provide a paint having goodcompatibility with the polymer with which it will be in contact, inorder to be sure of good adherence between glass and polymer in thepaint zone.

It is also possible to opacify the border of one of the PVB plies in anintermediate film of the PVB/PET/PVB type, and even to color itthroughout. It is in fact advantageous to use already existing plies ofthe PVB type which are provided at the periphery with a strip coloredthroughout, especially in blues or greens, possibly with a gradation ofcolor, especially toward the interior of the ply.

By such masking it is ensured that, once mounted, slightly clearerzones, of slightly different shade corresponding to the “margined”zones, cannot be distinguished at the periphery of the laminated glazingunit from the ply provided with the layer or layers. However, this isnot indispensable at the esthetic level: in fact, the invention makes itpossible to obtain a very sharp, very precise “transition”, whichultimately is esthetic in itself, which does not necessarily have to beconcealed.

A particularly preferred embodiment according to the invention comprisesmanufacturing a laminated glazing unit made of two glass substratesassembled by a “three-layer” intermediate film, of which one layer is aPET ply provided with at least one infrared-reflecting layer of themetallic type, disposed between two plies of thermoplastic polymer ofthe PVB type, the ply and its layer being set back from the edge wallsof the two glass plates and these two thermoplastic plies acting bymutual adhesion to seal the periphery from the outside. In fact,assembly of a laminated glazing unit is generally achieved by heatingand application of pressure, especially by passing the preassembledglazing unit through an autoclave: in fact, when the edges of the twoPVB plies become tacky and soft, they become unified in the peripheralzone where the ply of PET type has been margined, perfectly sealing inthe reflecting layer.

As mentioned hereinabove, elements of types such as elements ofconnection circuitry, sensors, antennas, electronic elements areinserted if desired in these “set-back” zones and/or in the “windows”cut in or at the edge of the ply of PET type, such elements thus being“embedded” in the PVB or at the PVB/glass interface.

Another object of the invention is a process for manufacture of the sametype of glazing unit, which meets the same criteria as for the precedingprocess and which represents a special embodiment thereof.

This second process includes the following stages:

-   -   a)—the intermediate film in “complete” form or already        containing at least the ply provided with the thin layer or        layers is cut to dimensions essentially identical to or larger        than those of at least one of the two substrates (stage        identical to that of the first process),    -   b)—the intermediate film is incised through at least the        thickness of the ply provided with the thin layer or layers, one        “inside” the other, in such a way as to define at least one zone        between these two lines,    -   c)—at least the ply provided with the thin layer or layers is        extracted from the intermediate film in this zone defined by the        two incision lines,    -   d)—the intermediate film is assembled in “complete” form between        the two substrates by adjoining thereto any polymer ply or plies        thereof which was or were missing in case it was not previously        in “complete” form (stage identical to stage c) of the first        process),    -   e)—the laminated glazing unit is then transformed (stage        identical to stage e) of the first process).

(The terminology is the same as for the preceding process).

By incision lines “one inside the other” there are understood here twolines such that the inner area defined by one of the two lines isdisposed completely inside the inner area defined by the other line. Infact, the PET ply of the intermediate film is not “margined” in thiscase, but instead there is extracted therefrom a border, a “trough” at adistance close to the edge wall of the intermediate film, said border,“trough,” corresponding to the zone of the ply which is located betweenthe two incision lines and which will be extracted before assembly. Thistherefore does not prevent the possibility that incipient corrosion ofthe thin layer or layers could develop on the external periphery of theglazing unit once it has been transformed, but such incipient corrosionwill be completely “stopped” by this trough, which creates in the layeror layers a sufficient discontinuity that propagation of corrosiontoward the central portion of the glazing unit is prevented. It may bepossible to mask the periphery of the glazing unit where traces ofcorrosion can develop, especially by an opacifying coating such as thosedescribed in the context of the first process.

In this specific embodiment, just as in the more general processaccording to the invention mentioned hereinabove, it must therefore beunderstood that, in the final glazing unit, the integrity of thefunctional layer is preserved in the zone of visibility of the glazingunit, with two kinds of forms in particular:

-   -   either the layer (and its support) is truly margined, in which        case the entire layer remaining in the final glazing unit is        protected,    -   or, by virtue of the trough described hereinabove, margining        does not take place, in the sense that the layer and its support        are not necessarily set back from the edge walls of the glass        plates of the final glazing unit, but the central zone of the        layer defined by the “innermost” incision line remains        integrated, while the zone of the layer outside the trough, or        in other words the extreme peripheral zone, is considered to be        “sacrificed” and no longer part proper of the        “operational”/“effective” functional layer within the meaning of        the invention.

The width of the “trough” can be adjusted as desired. It can assume theform of a strip of constant thickness, whose profile follows that of theedge walls of the glass plates, but in smaller proportions. It can alsobe of variable width, and in particular can be wider in the zones mostsusceptible to corrosive attack.

This trough can be extracted before assembly by manual or automatedmechanical pulling action. If the incision is made not only over thethickness of the ply provided with a layer or layers of the PET type butalso over the ply which covers it and which constitutes part of theintermediate film, for example of PVB, it may be preferable, onceextraction has been accomplished, to add a PVB strip of suitabledimensions in the extracted zone, so that the quality of lamination doesnot suffer from the presence of an intermediate film which is less thicklocally. This is not indispensable, however, especially when the widthof the “trough” is small, which is generally the case (on the order of 1to 3 mm, for example).

Another object of the invention is a process for manufacture of the sametype of glazing unit, which meets the same criteria as for the twopreceding processes.

This third process includes the following stages:

-   -   a′)—the intermediate film is cut to dimensions smaller than        those of the two glass substrates,    -   b′)—the intermediate film is positioned in contact with one of        the two glass substrates, in such a way that it is set back at        least in part from the edge walls of the glass plates,    -   c′)—one or more polymer-base strips, especially of thermoplastic        polymer of the PVB type, is or are disposed on the glass face        turned toward the intermediate film left bare where said ply is        set back,    -   d′)—this first glass plate provided with the intermediate film        and this strip or strips is assembled together with the second        glass plate, then the usual transformation to a laminated        glazing unit is effected.

In this case, “intermediate film” must be understood as the samestructure and nature of materials as in the scope of the precedingprocesses (of the type PVB/PET/layer or layers/PVB).

For stage (a′), there is chosen a size of intermediate film such thatthe desired margining is obtained de facto, generally in “standard”forms with square comers, although it is not prohibited from having amore complex, modulated profile.

For stage (c′), one or more strips of thermoplastic polymer is or areused in the margined zones, and they in fact act as a sealing peripheralseam which guarantees the imperviousness of the thin layer or layershaving thermal property or properties, and of the laminated glazing unitin general.

PVB-base strips are chosen which have optimal compatibility with thethermoplastic polymer plies of the intermediate film framing the plyprovided with the thin layer or layers which, as has been seenhereinabove, are also usually based on PVB. The strips can have a formexactly complementary to the form of the intermediate film in order tobe flush with the edge walls of the glass plates, or they can havesmaller dimensions and slightly simpler form: during assembly, thisstrip or these strips tend in fact to flow under the effect of heatand/or pressure and in doing so fill every available interstice, whileany “overhang” that may occur necessitates final trimming.

It is possible to attempt to achieve a maximum imperviousness effect byappropriately selecting the composition of this strip or these strips.Thus, although the base thereof may be PVB, its formulation has beenoptimized to reinforce its moisture-barrier properties, for example byinclusion of appropriate additives known to those skilled in the art.

This strip or these strips can be deposited either manually by anoperator or by an appropriate device, especially of automated type.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in more detail hereinafter by means ofnon-imitative embodiments with reference to the following figures:

FIG. 1: the laminated glazing unit, completely assembled according tothe first and second processes of the invention,

FIGS. 2 and 3: stages in manufacture of the glazing unit of FIG. 1according to the first process,

FIG. 4: one stage in the manufacture of the laminated glazing unitaccording to the second process,

FIG. 5: one stage in the manufacture of the laminated glazing unit ofFIG. 1 according to the third process of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

For more clarity, these figures are meant to be extremely schematic and,in particular, they do not represent the proportions between thedimensions, especially the thicknesses, of the different materialsshown.

EXAMPLE 1

This example relates to FIGS. 1 to 3 and to the first process accordingto the invention. FIG. 1 represents a section through the completedlaminated glazing unit 10. It is a vehicle windshield. Therein there areseen the two rigid substrates 1, 2 of soda-lime glass with thickness ofapproximately 2 to 3 mm, assembled by an intermediate film 3 comprisinga central ply 5 of PET, which is coated on one of its faces by a coating7 having solar protection properties, and which is disposed between twoPVB plies 4, 6. The two glass plates 1, 2, shown as plane, can in factbe curved:

-   -   PET ply 5 has a thickness of 50 μm,    -   each of the two PVB plies 4, 6 has a thickness of 0.38 mm,    -   coating 7 comprises a first layer of dielectric material of the        In₂O₃ type, topped by a reflecting layer of silver, in turn        topped by a layer of dielectric material of the In₂O₃ type. This        type of stack is described with more details in, for example,        International Patent WO-92/10632, and it has a square ohmic        resistance of about 4 ohm/square.    -   PET ply 5 is margined for a distance (d) (variable distance)        over its entire periphery relative to the edge walls of the two        glass plates 1, 2.

On the face of PVB ply 4 turned toward the glass plate 2 there can beinlaid a network of heating wires 15 with its ad hoc current collectors16.

In the margined zone of PET ply 5 provided with coating 7, the two PVBplies 4, 6 have been unified to form an impervious seam 12.

The process of manufacture of such a glazing unit takes place in thefollowing sequence:

-   -   As shown in section by FIG. 2, the intermediate film 3 cut to        dimensions almost identical to those which it must have to be        just flush with the edge walls of the glass plates 1, 2 once it        is positioned therebetween is placed in position on an        appropriate reference surface S. A cutting tool, of which merely        the slicing blade 13 is shown, and which is positioned relative        to the said surface S (or relative to the reference surface S′        following the external face of PVB ply 6), is made to incise the        thickness of the “upper” PVB ply 6 and that of the ply 5        provided with its coating 7. As shown in FIG. 3, once the        intermediate film has been incised, seen from above, this line I        follows the periphery c of the edge wall of the intermediate        film 3, in smaller proportions, in such a way as to define a        peripheral zone 8 of variable width p, defining in particular        two rounded “enclaves” 8′ and 8″ at the level of two of the        edges of the intermediate film. A window 8′″ is also provided,        by incision to the same depth along a closed line I′. There is        also provided a “starting tab” 9 in the extension of the        smallest edge of the intermediate film 3, or in other words a        small surface designed to “overhang” the glazing unit once the        intermediate film 3 has been positioned between the two glass        plates 1, 2, together with an incision line I″ designed to        facilitate “tearaway” of this tab during detachment of zone 8.        The window 8′″, or in other words the incised zone of ply 5 and        PVB ply 4, is then manually detached and then, at the position        of the window, there is added a PVB “patch” of size adjusted to        the dimension of zone 8′″, in such a way as to preserve        substantially uniform thickness of the intermediate film 3.        (Another solution consists, for example, in incising only ¾ of        the periphery I′, removing the incised PVB zone 6, completely        pulling off the zone of ply 5 corresponding to the window, then        replacing the incised PVB zone 6. There is then no reason to add        the preceding “patch”, since the thickness of intermediate film        3 has been substantially maintained). The intermediate film 3        incised in this way is then positioned between the two glass        plates 1, 2. These three elements are held in position, then the        starting tab 9 is pulled, with the result that the peripheral        zone 8 solely of the PET ply 5 provided with its coating 7 is        detached from the glazing unit. To facilitate this operation, it        is possible to provide a second starting tab, preferably located        in the corner diametrically opposite the first. The peripheral        zone of PVB ply 6, which has itself been incised, remains in        place because of the fact that it adheres more strongly to the        glass plate 1 than to PET 5, even before any true transformation        operation.

In this way, PET ply 5 has been margined in a completely modulablemanner. For example, the rounded enclave 8′ has a form designed suchthat, in this zone, an element of the sensor or chip type can beinserted between glass plate 1, 2 and intermediate film 3, the enclave8″ can correspond advantageously to the zone of the junction between thecollectors 16 and the current leads, and the window 8′″ can permit theinsertion of a sensor for remote toll-charge recording or of a G.P.S.antenna. In this way the coating 7 “avoids” any contact with thesesensors and zones of electric junction and, in general, outlines all thezones most susceptible to being attacked, especially by moisture.

EXAMPLE 2

This second example relates to the second process of the invention,which uses technical means quite similar to those of the first process,as shown in FIG. 4.

The difference lies in the manner in which the thickness of the assemblycomprising PET(5)/layers(7)/PVB(7) shown in FIG. 2 is incised; in thiscase, two closed incision lines I₁ and I₂ are made, incision line I₂being disposed inside the area defined by incision line I₁ , so as tocreate a zone 15 disposed between lines I₁ and I₂. FIG. 4 represents thesimplest embodiment, wherein this zone 15 has the form of a narrow stripof constant width “following” the edge of the intermediate film 3.Incision I₁ is made at approximately 4 to 8 mm from the edge of theintermediate film, especially at 6 mm, while incision I₂ is made in sucha way that the zone 15 has a minimum width of 1 mm and especially ofapproximately 1 to 2 mm.

Once the two incision have been made, this zone 15, which thereforecomprises the stack of PET/layers/PVB, is then extracted, thus creatinga “trough” in the intermediate film and assuring a discontinuity in thelayers (7).

The next step is the customary process of assembly and transformation ofthe glazing unit. The obtained glazing unit, in contrast to thataccording to FIG. 1, therefore contains a PET play and a flush coating7, but with a discontinuity at the level of extracted zone 15, thuspreventing propagation of corrosion from the edge of the glazing unit.In this case the extracted zone 15 has a width x of hardly 1 mm, whichis therefore of sufficiently small size that the reduced thickness ofthe intermediate film at this position does not cause any defect inlamination of the glazing unit. The following options are also possible:

-   -   either to make the incisions only on the “incomplete”        intermediate film devoid of the last PVB layer 7, which will be        added at a later time,    -   or to make the incisions on the “complete” intermediate film        and, after extraction of the zone 15, to add a little polymer to        preserve an almost constant thickness of the intermediate film.

EXAMPLE 3

According to the third process of the invention, there is obtained alaminated glazing unit quite similar to the first, with the sameelements. The difference lies in the nature of the impervious seam 12according to FIG. 1. In this case the seam is of inlaid nature, whichdoes not originate, or not exclusively, from flow of the two PVB plies4, 6, and the chemical composition of which has been selected to beparticularly impervious to liquid water and water vapor.

The manufacture process takes place in the following manner:

-   -   the entire intermediate film 3 is initially cut out to        dimensions smaller than those of glass plates 1 and 2, with        square corners,    -   then, as shown in FIG. 5, the intermediate film 3 is positioned        on the first glass plate 2, then an “impervious” PVB strip 14 is        placed in the glass zones left exposed. For more simplicity,        this strip can be of simple geometric form, which is obtained,        for example, from a ribbon of parallelepiped section and        adequate thickness relative to that of the intermediate film,        which ribbon is positioned around the intermediate film 3. It        could also comprise four strips, one for each of the edges left        exposed. During transformation, this strip 14 flows to occupy        the entire interstice left free by intermediate film 3 between        glass plates 1, 2. In fact, intermediate film 3 is dimensioned        specifically to ensure that its dimensions are equal to those of        the glass plate 2 less the width of strip 14 used.

After this strip 14 has been positioned, the only steps remaining are toposition the second glass plate 1, then to proceed with assembly bycustomary techniques.

It must be noted that the junction zone 17 between the start and end ofstrip 14 is preferably oblique relative to the edges of glass plates 1,2, to guarantee good imperviousness at this level, even in the case of ajunction that is not completely continuous.

According to the first, second or third process, the laminated glazingunit according to the invention, by virtue of coating 7, exhibitsinteresting solar protection properties: it can have light transmissionvalues T_(L) on the order of 76 to 78%, light reflection values R_(L) ofat most 10%, energy transmission values T_(E) of at most 50% andinfrared reflection values greater than 45% (measured with the D₆₅illuminant).

1. A process for manufacture of a laminated glazing unit comprising atleast two glass substrates assembled by an intermediate film having atleast one ply based on a polymer or polymers provided on at least one ofits faces with a functional thin layer or a stack of functional thinlayers having properties of reflection in infrared, wherein the processincludes the following steps: a)—the intermediate film alreadycontaining at least the ply provided with the thin layer or the stack ofthin layers is cut to dimensions larger than at least one of the twoglass substrates, b)—the intermediate film is incised through at least athickness of the ply provided with the thin layer or the stack of thinlayers having properties of reflection in infrared, in such a way as todefine at least one peripheral zone or zones of said ply localizedbetween an incision line and an edge of the ply, c)—the intermediatefilm is assembled between the two glass substrates by adjoining theretoany polymer ply or plies thereof which was or were missing, d)—theperipheral zone or zones of the ply is or are detached by pulling it onthem mechanically, e)—the laminated glazing unit is transformed, thesteps taking place in the above order.
 2. A process according to claim1, wherein the incision line is made by stamping or by cutting with amovable tool provided with a slicing element or a laser.
 3. A processaccording to claim 1, wherein the thin layer or the stack of thin layershaving properties of reflection in the infrared is or are provided withan electricity supply to give the layer or the layers heatingcapability.
 4. A process according to claim 1, wherein at least one ofthe faces of at least one ply which constitutes the intermediate filmand which is not in contact with the thin layer or the stack of thinlayers having properties of reflection in the infrared is provided witha network of heating wires.
 5. A process according to claim 1, whereinthe incision line at least partly follows, in smaller proportions, aprofile similar or identical to that of edge walls of the glasssubstrates.
 6. A process according to claim 1, wherein, before assembly(c), the intermediate film is also incised through at least thethickness of the ply provided with the thin layer or the stack of thinlayers, in such a way as to define a line which is closed on itself,thus allowing windows to be created.
 7. A process according to claim 1,wherein the ply is based on flexible polymers of linear polyester.
 8. Aprocess according to claim 7, wherein the linear polyester is one ofpolyethylene terephthalate (PET), polycarbonate, polypropylene,polyethylene, polyether sulfide, polysulfide and polymethacrylate.
 9. Aprocess according to claim 1, wherein the intermediate film comprises aplurality of polymer plies, wherein in particular the ply provided withthe layer or the stack of thin layers having properties of reflection inthe infrared is disposed between two plies based on thermoplasticpolymers.
 10. A process according to claim 9, wherein the thermoplasticpolymers are one of polyvinyl butyral (PVB) and polyurethane (PU).
 11. Aprocess according to claim 1, wherein the intermediate film comprises aplurality of plies based on a polymer or polymers, and wherein the plyprovided with the thin layer or the stack of thin layers havingproperties of reflection in the infrared is incised during step (b). 12.A process according to claim 11, wherein only the peripheral zone orzones of the ply provided with the layer or the stack of thin layershaving properties of reflection in the infrared is or are detachedduring step (d).
 13. A process according to claim 1, wherein theperipheral zone or zones of the ply is or are designed such as tooverhang locally edge walls of the glass substrates.
 14. A processaccording to claim 13, wherein the peripheral zone or zones of the plyis or are designed in a form of a starting tab or tabs on whichmechanical pulling action is exerted to detach the peripheral zone orzones during step (d).
 15. A process according to claim 1, wherein thethin layer or the stack of thin layers comprises at least one layerbased on at least one metal belonging to the group comprising: silver,copper, indium, gold, nickel, chromium, aluminum, tantalum, niobium, orbased on at least one doped metal oxide.
 16. A process according toclaim 15, wherein the at least one doped metal oxide is one of tin oxidedoped with fluorine (SnO₂:F), indium oxide doped with tin (ITO) andmetal nitride of the types TiN and ZrN.
 17. A process according to claim1, wherein the incision line defines a continuous peripheral zone on aply in such a way that, once assembly has been completed, there exists,between the edge of the ply and edge walls of the glass substrates, amargin which is always at least 3 mm.
 18. A process according to claim17, wherein the margin is about 6 mm.
 19. A process according to claim1, wherein the incised peripheral zone or zones of the ply defined bythe incision line designed so as to enclose elements designed to beinserted between the glass substrates and the intermediate film in thelaminated glazing unit, so as to create windows to allow electromagneticwaves to pass there through.
 20. A process according to claim 19,wherein the elements designed to be inserted include one of elements ofconnection circuitry, elements of a current-lead type, volumetricsensors, moisture sensors, electronic chips and radio antennas.
 21. Aprocess according to claim 1, wherein all or part of a zone or zones ofthe intermediate film corresponding to the peripheral zone or zonesdetached from the ply during step (d) are masked by an opacifyingcoating.
 22. A process according to claim 21, wherein the opacifyingcoating is applied by one of depositing enamel on an outer or inner faceof at least one of the glass substrates, silk-screen printing of ink onat least one of the faces of the at least one ply of the intermediatefilm, and by coloring a border of the at least one ply throughout in aform of a strip of graduated coloration.